/*
 *   Copyright 2008 Francois Fernandes
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */
package com.googlecode.jobjectlife.internal;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.util.Map;

import com.googlecode.jobjectlife.ILifecycleState;
import com.googlecode.jobjectlife.ObjectLifecycleManager;

public class ManagedObjectInvocationHandler implements InvocationHandler
{

    private final Map<Method, MethodCallConfiguration> configuration;

    private final ObjectLifecycleManager<ILifecycleState> manager;

    private final Object managedObject;

    public ManagedObjectInvocationHandler( Object managedObject, ObjectLifecycleManager<ILifecycleState> manager,
                                           Map<Method, MethodCallConfiguration> configuration )
    {
        this.manager = manager;
        this.configuration = configuration;
        this.managedObject = managedObject;
    }

    public Object invoke( Object proxy, Method method, Object[] args ) throws Throwable
    {

        MethodCallConfiguration mcfg = configuration.get( method );
        if ( mcfg != null )
        {
            ILifecycleState s = mcfg.getRequiredState();

            if ( s != null )
            {
                ILifecycleState currentState = manager.getCurrentState();
                if ( currentState != s )
                {
                    throw new IllegalStateException( "object is in illegal state: "
                                    + ( currentState != null ? currentState.name() : "null" ) + ". Expected state: "
                                    + ( s != null ? s.name() : "null" ) );
                }
            }

        }

        Object result = method.invoke( managedObject, args );

        if ( mcfg != null )
        {
            ILifecycleState target = mcfg.getTransitionAfterTarget();

            if ( target != null )
            {
                manager.transition( target );
            }
        }

        return result;
    }

}
